To meet recent demands for use on vehicles in consideration of environmental issues or for employing DC power supplies for large tools, small and lightweight secondary batteries capable of performing rapid charge and large-current discharge have been required. Examples of typical batteries satisfying such demands include a nonaqueous electrolyte secondary battery employing, as a negative electrode material, an active material such as lithium metal or a lithium alloy or a lithium intercalation compound in which lithium ions are intercalated in carbon serving as a host substance (which is herein a substance capable of intercalating or deintercalating lithium ions), and also employing, as an electrolyte, an aprotic organic solvent in which lithium salt such as LiClO4 or LiPF6 is dissolved.
This nonaqueous electrolyte secondary battery generally includes: a negative electrode in which the negative electrode material described above is supported on a negative electrode current collector; a positive electrode in which a positive electrode active material, e.g., lithium cobalt composite oxide, electrochemically reacting with lithium ions reversibly is supported on a positive electrode current collector; and a porous insulating layer carrying an electrolyte thereon and interposed between the negative electrode and the positive electrode to prevent short-circuit from occurring between the negative electrode and the positive electrode.
The positive and negative electrodes formed in the form of sheet or foil are stacked, or wound in a spiral, with the porous insulating layer interposed therebetween to form a power generating element. This power generating element is placed in a battery case made of metal such as stainless steel, iron plated with nickel, or aluminium. Thereafter, the electrolyte is poured in the battery case, and then a lid is fixed to the opening end of the battery case to seal the battery case. In this manner, a nonaqueous electrolyte secondary battery is fabricated.
Patent Document 1: Japanese Unexamined Patent Publication No. 5-182692.